GFF5.qxd 14/11/06 16:44 Page 93 PA RT I I I Fortificants: physical characteristics, selection and use with specific food vehicles GFF5.qxd 14/11/06 16:44 Page 94 GFF5.qxd 14/11/06 16:44 Page 95 Introduction By providing a critical review of the fortificants that are currently available for fortification purposes, Part III of these guidelines is intended to assist pro- gramme managers in their choice of firstly, a suitable food vehicle and secondly, a compatible fortificant. Having established – through the application of appro- priate criteria – that the nature of the public health risk posed by a micronutri- ent deficiency justifies intervention in the form of food fortification, the selection of a suitable combination of food vehicle and fortificant(s), or more specifically, the chemical form of the micronutrient(s) that will added to the chosen food vehicle, is fundamental to any food fortification programme. Subsequent chap- ters (Part IV) cover other important aspects of food fortification programme planning, including how to calculate how much fortificant to add to the chosen food vehicle in order to achieve a predetermined public health benefit (Chapter 7), monitoring and impact evaluation (Chapters 8 and 9), marketing (Chapter 10) and regulatory issues (Chapter 11). In practice, the selection of a food vehicle–fortificant combination is governed by range of factors, both technological and regulatory. Foods such as cereals, oils, dairy products, beverages and various condiments such as salt, sauces (e.g. soy sauce) and sugar are particularly well suited to mandatory mass fortifica- tion. These foods share some or all of the following characteristics: • They are consumed by a large proportion of the population, including (or especially) the population groups at greatest risk of deficiency. • They are consumed on a regular basis, in adequate and relatively consistent amounts. • They can be centrally processed (central processing is preferable for a number of reasons, but primarily because the fewer the number of locations where fortificants are added, the easier it is to implement quality control meas- ures; monitoring and enforcement procedures are also likely to be more effec- tive). • Allow a nutrient premix to be added relatively easily using low-cost technol- ogy, and in such a way so as to ensure an even distribution within batches of the product. 95 GFF5.qxd 14/11/06 16:44 Page 96 GUIDELINES ON FOOD FORTIFICATION WITH MICRONUTRIENTS • Are used relatively soon after production and purchase. Foods that are pur- chased and used within a short period of time of processing tend to have better vitamin retention, and fewer sensorial changes due to the need for only a small overage1. The choice of fortificant compound is often a compromise between reasonable cost, bioavailability from the diet, and the acceptance of any sensory changes. When selecting the most appropriate chemical form of a given micronutrient, the main considerations and concerns are thus: • Sensory problems.Fortificants must not cause unacceptable sensory problems (e.g. colour, flavour, odour or texture) at the level of intended fortification, or segregate out from the food matrix, and they must be stable within given limits. If additional packaging is needed to improve stability of the added for- tificant, it is helpful if this does not add significantly to the cost of the product and make it unaffordable to the consumer. • Interactions. The likelihood or potential for interactions between the added micronutrient and the food vehicle, and with other nutrients (either added or naturally present), in particular any interactions that might interfere with the metabolic utilization of the fortificant, needs to be assessed and checked prior to the implementation of a fortification programme. • Cost. The cost of fortification must not affect the affordability of the food nor its competitivity with the unfortified alternative. • Bioavailability. The fortificant must be sufficiently well absorbed from the food vehicle and be able to improve the micronutrient status of the target population. Safety is also an important consideration. The level of consumption that is required for fortification to be effective must be compatible with a healthy diet. The following two chapters consider the above factors in relation to specific micronutrients or micronutrient groups. Chapter 5 deals with iron, vitamin A and iodine; Chapter 6 covers some of the other micronutrients (such as zinc, folate and the other B vitamins, vitamin D and calcium) for which the severity of the public health problem of deficiencies is less well known but is believed to be significant. The discussion is limited to those fortificants and food vehicles that currently are the most widely used, or that have potential for wider appli- cation. Details of publications and articles containing more in-depth informa- tion about the fortification of foods with specific nutrients are provided in the attached further reading list. 1 Overage is the term used to describe the extra amount of micronutrient that is added to a food vehicle to compensate for losses during production, storage, distribution and selling. 96 GFF5.qxd 14/11/06 16:44 Page 97 CHAPTER 5 Iron, vitamin A and iodine 5.1 Iron 5.1.1 Choice of iron fortificant Technically, iron is the most challenging micronutrient to add to foods, because the iron compounds that have the best bioavailability tend to be those that inter- act most strongly with food constituents to produce undesirable organoleptic changes. When selecting a suitable iron compound as a food fortificant, the overall objective is to find the one that has the greatest absorbability, i.e. the highest relative bioavailability1 (RBV) compared with ferrous sulfate, yet at the same time does not cause unacceptable changes to the sensory properties (i.e. taste, colour, texture) of the food vehicle. Cost is usually another important consideration. A wide variety of iron compounds are currently used as food fortificants (Table 5.1). These can be broadly divided into three categories: (224–226) —water soluble; — poorly water soluble but soluble in dilute acid; —water insoluble and poorly soluble in dilute acid. 5.1.1.1 Water-soluble compounds Being highly soluble in gastric juices, the water-soluble iron compounds have the highest relative bioavailabilities of all the iron fortificants and for this reason are, more often than not, the preferred choice. However, these compounds are also the most likely to have adverse effects on the organoleptic qualities of foods, in particular, on the colour and flavour. During prolonged storage, the presence of fortificant iron in certain foods can cause rancidity and subsequent off- flavours. Moreover, in the case of multiple fortification, free iron, produced from the degradation of iron compounds present in the food, can oxidize some of the vitamins supplied in the same fortificant mixture. 1 Relative bioavailability is a measure which scores the absorbability of a nutrient by comparing its absorbability to that of a reference nutrient that is considered as having the most efficient absorbability. 97 GFF5.qxd 14/11/06 16:44 Page 98 GUIDELINES ON FOOD FORTIFICATION WITH MICRONUTRIENTS TABLE 5.1 Key characteristics of iron compounds commonly used for food fortification purpose: solubility, bioavailability and cost Compound Iron content Relative bioavailabilitya Relative costb (%) (per mg iron) Water soluble Ferrous sulfate. 7H2020 100 1.0 Ferrous sulfate, dried 33 100 1.0 Ferrous gluconate 12 89 6.7 Ferrous lactate 19 67 7.5 Ferrous bisglycinate 20 >100c 17.6 Ferric ammonium citrate 17 51 4.4 Sodium iron EDTA 13 >100c 16.7 Poorly water soluble, soluble in dilute acid Ferrous fumarate 33 100 2.2 Ferrous succinate 33 92 9.7 Ferric saccharate 10 74 8.1 Water insoluble, poorly soluble in dilute acid Ferric orthophosphate 29 25–32 4.0 Ferric pyrophosphate 25 21–74 4.7 Elemental iron – – – H-reduced 96 13–148d 0.5 Atomized 96 (24) 0.4 CO-reduced 97 (12–32) <1.0 Electrolytic 97 75 0.8 Carbonyl 99 5–20 2.2 Encapsulated forms Ferrous sulfate 16 100 10.8 Ferrous fumarate 16 100 17.4 EDTA, ethylenediamineteraacetate; H-reduced, hydrogen reduced; CO-reduced, carbon monoxide reduced. a Relative to hydrated ferrous sulfate (FeSO4.7H2O), in adult humans. Values in parenthesis are derived from studies in rats. b Relative to dried ferrous sulfate. Per mg of iron, the cost of hydrated and dry ferrous sulfate is similar. c Absorption is two-three times better than that from ferrous sulfate if the phytate content of food vehicle is high. d The high value refers to a very small particle size which has only been used in experimental studies. Sources: adapted from references (224–226), with additional data supplied by P. Lohmann (cost data) and T. Walczky (ferrous lactate, H-reduced elemental iron). The water-soluble forms of iron are especially suited to fortifying cereal flours that have a relatively fast turnover, i.e. one month in warm, humid climates and up to 3 months in dry, cold climates. Water-soluble iron compounds are also useful for dry foods, such as pasta and milk powder, as well as dried milk-based infant formulas. Encapsulated forms, i.e. iron compounds that have been coated 98 GFF5.qxd 14/11/06 16:44 Page 99 5. IRON, VITAMIN A AND IODINE to physically separate the iron from the other food components, can be used for slowing down or preventing sensory changes. Ferrous sulfate is by far the most frequently used water-soluble iron fortifi- cant, principally because it is the cheapest. It has been widely used to fortify flour (see section 5.1.5.1). However, depending on its physical characteristics, the climate and the fat content of the flour to which it is added, ferrous sulfate can cause rancidity, and therefore its suitability as a fortificant needs to be eval- uated in trials before use.